At present, electrode-catalysts for a direct methanol fuel cell used by a commercial company or a R/D center mostly use a carbon black from the Cabot Company (Vulcan XC-72, with a surface area of about 250 m2/g) as a carrier. Vulcan XC-72 is an electrically conductive material, which has been used for over 30 years. The potential defects of Vulcan XC-72 include a low surface area, and liable to cause an excessive particle size of the activation center and a relatively low loading ratio for an electrode-catalyst requiring a high loading. For example, the average particle size of the activation center of a Pt/Carbon catalyst having 10 wt % Pt deposited on a carbon black carrier Vulcan XC-72 with a surface area of about 250 m2/g is 2.0 nm; the values are 3.2 and 8.8 nm, separately, when the content of the Pt ingredient is increased to 30 wt % and 60 wt %, respectively. This finding indicates that an increase on the metal loading of a catalyst does not necessarily increase the surface area of the catalyst's activation center. In order to increase the metal loading and maintain a small particle size, studies must be emphasized on increasing the surface area of the carrier and improving the synthesis method of the carrier. One of the methods in making a breakthrough on the current direct methanol fuel cell is to develop a new carbon material with a higher surface area, a more uniform porosity distribution, and a higher electrical conductivity.
In 1992 researchers at Mobil Corp. (U.S. Pat. No. 5,108,725) disclosed a new family of crystalline mesoporous materials, M41S. These mesoporous molecular sieves with adjustable and uniformed pore sizes in the range of 1.5 to 10.0 nm cover a new range of potential applications. One member of this series, MCM-41, possessing a hexagonal arrangement of uniformly sized channel mesopores, has been the focus of most recent applications as catalysts and sorbents. The disclosure in U.S. Pat. No. 5,108,725 is incorporated herein by reference. Heretofore, mesoporous molecular sieves synthesized include M41S series, and SBA series, etc., the pore (channel) sizes range from 1.5 to 30 nm.
A direct methanol fuel cell generates power by converting the chemical energy in methanol into electric energy and involves gas-liquid-solid three phase reactions. Other than increasing the surface area of a catalyst's activation center, the catalyst's activity is also affected by the mass transfer rate of methanol and the capability in discharging the carbon dioxide generated by the reactions. Therefore, the pore size, sterical structure and surface properties (surface functional groups, hydro-affinity, etc.) of a carbon carrier have a significant influence on the performance of a cell. Thus, research on the carbon material is one of the key factors in increasing the performance of a fuel cell.